BARCELONA, Spain -- It is six years since a team without Lionel Messi or Cristiano Ronaldo won the Champions League and, if you conducted a straw poll of the Manchester United team torn apart by Barcelona's magician in the Nou Camp during a 3-0 quarterfinal second-leg defeat Tuesday night, few responses would suggest the sequence will end this season.

Ronaldo, courtesy of Ajax's stunning victory against Juventus, will not be in Madrid for the final June 1, but Messi, who netted twice in four minutes against United, is still on course to get his hands on the European Cup for a fifth time, which would equal the winners' medal tally of his great rival in the process.

Liverpool are likely to be Barcelona's semifinal opponents -- Jurgen Klopp's side lead FC Porto 2-0 going into Wednesday's return leg in Portugal -- and will believe they can slam the brakes on the Catalan club's juggernaut and deny Messi & Co. a symbolic European Cup triumph in the Spanish capital.

But while Ernesto Valverde's Barcelona are not in the same stratosphere as Pep Guardiola's 2008-12 vintage, which won two Champions Leagues, or Luis Enrique's 2015 Treble winners, the presence of Messi means they boast the most potent weapon of any side still harbouring hopes of glory this season.

Moreover, the great man is on a personal mission to win it again, having promised supporters at the start of this season that the squad was determined to bounce back from last season's humbling quarterfinal exit against Roma, which came in spite of Barcelona winning the first leg 4-1.

"Last season was really good as we did the double, but we all felt bad about how it went in the Champions League," Messi said eight months ago to the day, on Aug. 16. "We promise that this season we will do all we can to bring that beautiful trophy back to the Camp Nou."

In the event that Liverpool do provide their next opposition, Barcelona will be given a tougher test by than that provided by United.

Lionel Messi was unstoppable vs. Man United, and he can lead Barcelona to more Champions League glory. AP

But regardless, Barcelona will still have Messi to get them out of any hole, and that is why Valverde's men will be favourites to reach, and win, the final at Atletico Madrid's Wanda Metropolitano Stadium. As Solskjaer himself said: "You can prepare all you like, but if you give him (Messi) time and space around the goal, he will score. He's a fantastic player."

So much of what Barcelona do carries Messi's unique mark of genius, and he effectively ended the tie vs. United in a four-minute spell just after the quarter-hour mark.

His first goal was all about opportunism, as he pounced on a mistake by Ashley Young to steal the ball, before nutmegging Fred and skipping into space on the edge of the penalty area. Then came the move and shot seen countless times over the past 15 years: a cut inside onto his left foot, followed by an unerring strike into the bottom corner.

Everyone knows what is coming, but nobody has shown themselves able to stop it, and David De Gea was beaten like so many keepers before him.

Moments later it was two, thought this time United were more responsible for their own downfall. First, another failure by the away side to keep possession gave Messi a chance to capitalise and, second, De Gea inexplicably allowed a weak effort to squirm under his body and into the net.

For a goalkeeper yet to sign a new contract at United, it was hardly the best audition for a move back to his native Spain, where his reputation has already been tarnished by uninspired international performances. Maybe De Gea was spooked by Messi's first goal and caught expecting something else, but it was nevertheless a calamitous mistake.

Messi, though, is about more than goals. Six days ago at Old Trafford, he was subdued by his own standards after having his nose bloodied in a challenge with Chris Smalling, but here he toyed with United -- Young and Phil Jones in particular -- and strode across the pitch like a man in his own universe. Indeed, one young fan held a board which read, "Messi, before you go back to space, can I have your shirt?"

Before he headed back to his own planet, Messi still had business to finish, and his long-range pass to Jordi Alba on 61 minutes led to Philippe Coutinho's 20-yard curler, which put the home side 3-0 in front on the night and 4-0 on aggregate. Three minutes later, Messi was inches away from claiming his hat trick with an overhead kick.

Make no mistake, the brilliance of their talisman masks glaring problems for this Barcelona team -- Luis Suarez's lack of mobility and sharpness, Sergio Busquets' recklessness and Coutinho's inconsistency could prove costly -- but he is a decent sticking plaster to have.

Injury or suspension would change things, yet while Messi is playing, Barcelona are the team to beat.